Electrochemical degradation of hydrolyzed polyacrylamide by a novel La-In co-doped PbO2 electrode: Electrode characterization, influencing factors and degradation pathway

Abstract

• A novel La-In-PbO 2 co-doped electrode was prepared through electrodeposition. • The electrode presents compact pyramidal structure with large surface area. • The modification enhances the oxygen evolution potential and the stability of the electrode. • Hydrolyzed polyacrylamide can be degraded effectively. The anode materials play a key role in the electrochemical oxidation process. In this work, a new type of Ti/Sn-SbO x /α-PbO 2 /La-In-β-PbO 2 electrode has been prepared through electrodeposition and applied to the degradation of high concentration aqueous solution of hydrolyzed polyacrylamide (HPAM). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Energy-dispersive spectroscopy (EDS) were employed to characterize the surface morphological and structural properties of the electrodes, which indicated that the La-In-PbO 2 electrode had smaller grain size, denser surface and larger active surface area compared with undoped and single-doped PbO 2 electrode. Cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were also utilized to investigate the electrochemical performance of electrodes. The results showed that the La-In-PbO 2 electrode exhibited higher oxidation peak current, oxygen evolution potential (2.22 V) and lower charge transfer resistance. The La-In-PbO 2 electrodes were used as anode to degrade HPAM solution under different conditions. The results revealed that the viscosity reduction rate of HPAM reached to 97.63 % after 60 min under the condition of electrolyte concentration, initial concentration of HPAM, initial pH and current density were 0.05 M, 3 g·L −1 , 7 and 20 mA·cm −2 , respectively. The kinetic behavior of HPAM degradation was analyzed by the viscosity reduction experiment. The intermediates in the electrochemical oxidation process were identified by GC–MS and the possible degradation mechanism of HPAM was explored by UV–visible absorption spectra and the Fourier Transform Infrared (FT-IR) spectra.